SmogRank / Episodes / Thailand

North-western Thailand, May 2023

For 1 day, on 26 May 2023, 17 cities in Thailand had PM2.5 at least twice their usual for the time of year. The worst reading was Khan Na Yao, Bangkok, Thailand: 34.3 µg/m³ on 26 May, about 2.0× its usual 16.9.

No cause namedWe have no fire or smoke records for these days, so we only say what the measurements show.
Cities reached17in 1 country
Days126 May 2023
Worst day26 May17 cities counted
Furthest above usual3.1×Kamphaeng Phet

Day by day

26 May 17 cities at twice their usual or more
PhichitNakhon SawanTakLoeiChai NatChaiyaphumNanNong Bua LamphuLamphunSaraburiTha BoUdon ThaniVientianeKhlong LuangSai MaiLak SiMueang NonthaburiKhlong Sam WaNong ChokNakhon PathomBueng KumSaphan SungBangkokSi Maha PhotNong KhaemBan Khlong PrawetLat KrabangPhra PradaengBang NaBan Samae DamSamut SakhonBang Bo DistrictRatchaburiBuri RamRoi EtBan HouakhouaLaem ChabangPakxanAranyaprathetYangonSi Sa KetKhan Na YaoBang KapiNakhon RatchasimaSing BuriSuphan BuriLop BuriChiang MaiPhra Nakhon Si AyutthayaSamut PrakanUttaraditLampangMae SotPhraePhetchabunChiang RaiSukhothaiKamphaeng Phet
23 May242526272829
Every measured city in the area, coloured by its PM2.5 that day; a dark ring marks a city at twice its usual or more. Bars: cities counted each day, coloured by their median level. Choose a day or press play; without JavaScript, the days link to that day's world ranking.

How it spread

Bang KapiBang Kapi, 23 May: 23.6 µg/m³, 1.8× usualBang Kapi, 24 May: 24.4 µg/m³, 1.9× usualBang Kapi, 25 May: 27.7 µg/m³, 2.1× usualBang Kapi, 26 May: 27.3 µg/m³, 2.1× usualBang Kapi, 27 May: 25.5 µg/m³, 2.0× usualBang Kapi, 28 May: 19.1 µg/m³, 1.5× usualBang Kapi, 29 May: 19.4 µg/m³, 1.5× usualKhan Na YaoKhan Na Yao, 23 May: no readingKhan Na Yao, 24 May: no readingKhan Na Yao, 25 May: 29.7 µg/m³, 1.8× usualKhan Na Yao, 26 May: 34.3 µg/m³, 2.0× usualKhan Na Yao, 27 May: no readingKhan Na Yao, 28 May: no readingKhan Na Yao, 29 May: no readingNakhon RatchasimaNakhon Ratchasima, 23 May: no readingNakhon Ratchasima, 24 May: no readingNakhon Ratchasima, 25 May: no readingNakhon Ratchasima, 26 May: 34.0 µg/m³, 2.1× usualNakhon Ratchasima, 27 May: no readingNakhon Ratchasima, 28 May: no readingNakhon Ratchasima, 29 May: no readingLampangLampang, 23 May: no readingLampang, 24 May: no readingLampang, 25 May: no readingLampang, 26 May: 33.2 µg/m³, 2.3× usualLampang, 27 May: no readingLampang, 28 May: no readingLampang, 29 May: no readingPhraePhrae, 23 May: no readingPhrae, 24 May: no readingPhrae, 25 May: no readingPhrae, 26 May: 31.2 µg/m³, 2.4× usualPhrae, 27 May: no readingPhrae, 28 May: no readingPhrae, 29 May: no readingUttaraditUttaradit, 23 May: no readingUttaradit, 24 May: no readingUttaradit, 25 May: no readingUttaradit, 26 May: 31.2 µg/m³, 2.3× usualUttaradit, 27 May: no readingUttaradit, 28 May: no readingUttaradit, 29 May: no readingChiang RaiChiang Rai, 23 May: no readingChiang Rai, 24 May: no readingChiang Rai, 25 May: no readingChiang Rai, 26 May: 30.6 µg/m³, 2.9× usualChiang Rai, 27 May: no readingChiang Rai, 28 May: no readingChiang Rai, 29 May: no readingLop BuriLop Buri, 23 May: no readingLop Buri, 24 May: no readingLop Buri, 25 May: no readingLop Buri, 26 May: 29.4 µg/m³, 2.2× usualLop Buri, 27 May: no readingLop Buri, 28 May: no readingLop Buri, 29 May: no readingPhetchabunPhetchabun, 23 May: no readingPhetchabun, 24 May: no readingPhetchabun, 25 May: no readingPhetchabun, 26 May: 29.3 µg/m³, 2.7× usualPhetchabun, 27 May: no readingPhetchabun, 28 May: no readingPhetchabun, 29 May: no readingKamphaeng PhetKamphaeng Phet, 23 May: no readingKamphaeng Phet, 24 May: no readingKamphaeng Phet, 25 May: no readingKamphaeng Phet, 26 May: 27.2 µg/m³, 3.1× usualKamphaeng Phet, 27 May: no readingKamphaeng Phet, 28 May: no readingKamphaeng Phet, 29 May: no readingPhra Nakhon Si Ayut…Phra Nakhon Si Ayutthaya, 23 May: no readingPhra Nakhon Si Ayutthaya, 24 May: no readingPhra Nakhon Si Ayutthaya, 25 May: no readingPhra Nakhon Si Ayutthaya, 26 May: 26.2 µg/m³, 2.3× usualPhra Nakhon Si Ayutthaya, 27 May: no readingPhra Nakhon Si Ayutthaya, 28 May: no readingPhra Nakhon Si Ayutthaya, 29 May: no readingChiang MaiChiang Mai, 23 May: no readingChiang Mai, 24 May: no readingChiang Mai, 25 May: no readingChiang Mai, 26 May: 26.1 µg/m³, 2.2× usualChiang Mai, 27 May: no readingChiang Mai, 28 May: no readingChiang Mai, 29 May: no readingSing BuriSing Buri, 23 May: no readingSing Buri, 24 May: no readingSing Buri, 25 May: no readingSing Buri, 26 May: 26.1 µg/m³, 2.1× usualSing Buri, 27 May: no readingSing Buri, 28 May: no readingSing Buri, 29 May: no readingSamut PrakanSamut Prakan, 23 May: 22.4 µg/m³, 2.0× usualSamut Prakan, 24 May: 20.4 µg/m³, 1.8× usualSamut Prakan, 25 May: no readingSamut Prakan, 26 May: 25.9 µg/m³, 2.3× usualSamut Prakan, 27 May: 26.5 µg/m³, 2.3× usualSamut Prakan, 28 May: 19.6 µg/m³, 1.7× usualSamut Prakan, 29 May: 14.9 µg/m³, 1.3× usualSukhothaiSukhothai, 23 May: no readingSukhothai, 24 May: no readingSukhothai, 25 May: no readingSukhothai, 26 May: 25.5 µg/m³, 3.0× usualSukhothai, 27 May: no readingSukhothai, 28 May: no readingSukhothai, 29 May: no readingMae SotMae Sot, 23 May: no readingMae Sot, 24 May: no readingMae Sot, 25 May: no readingMae Sot, 26 May: 25.3 µg/m³, 2.3× usualMae Sot, 27 May: no readingMae Sot, 28 May: no readingMae Sot, 29 May: no readingSuphan BuriSuphan Buri, 23 May: no readingSuphan Buri, 24 May: no readingSuphan Buri, 25 May: no readingSuphan Buri, 26 May: 25.3 µg/m³, 2.1× usualSuphan Buri, 27 May: no readingSuphan Buri, 28 May: no readingSuphan Buri, 29 May: no reading23 May242526272829
Every counted city, in the order the episode reached them, 3 days before to 3 after. Each square is a day, coloured by that day's PM2.5; outlined: at twice the city's usual or more.
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

Every city it reached

CityDaysHighestUsualAbove usual
Kamphaeng PhetKamphaeng Phet, Thailand1 27.226 May8.83.1×
SukhothaiSukhothai, Thailand1 25.526 May8.63.0×
Chiang RaiChiang Rai, Thailand1 30.626 May10.52.9×
PhetchabunPhetchabun, Thailand1 29.326 May11.02.7×
PhraePhrae, Thailand1 31.226 May12.82.4×
Samut PrakanSamut Prakan, Thailand1 26.527 May11.42.3×
Phra Nakhon Si AyutthayaPhra Nakhon Si Ayutthaya, Thailand1 26.226 May11.32.3×
LampangLampang, Thailand1 33.226 May14.52.3×
Mae SotTak, Thailand1 25.326 May11.12.3×
UttaraditUttaradit, Thailand1 31.226 May13.72.3×
Lop BuriLopburi, Thailand1 29.426 May13.22.2×
Chiang MaiChiang Mai, Thailand1 26.126 May12.12.2×
Bang KapiBangkok, Thailand1 27.725 May12.92.1×
Nakhon RatchasimaNakhon Ratchasima, Thailand1 34.026 May16.12.1×
Sing BuriSing Buri, Thailand1 26.126 May12.52.1×
Suphan BuriSuphan Buri, Thailand1 25.326 May12.22.1×
Khan Na YaoBangkok, Thailand1 34.326 May16.92.0×

Daily means in µg/m³. Usual: the city's median for this time of year (its days within 21 days of the date, every year, leaving out the week around it). Above usual: its highest day against that.

Against other episodes in Thailand

Number 12 of 24 episodes in Thailand since our records began, by cities reached.

Bars: cities reached; colour: the level of the episode's highest daily reading. All 24.

Use this page

SmogRank, North-western Thailand, May 2023: 17 cities with PM2.5 at twice their usual or more, 26 May 2023, smogrank.com/episodes/2023-05-north-western-thailand-4 (accessed 3 October 2026).

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You're welcome to reuse a single chart, image or figure with this citation and a link. Terms.

An episode is a run of days when many cities close to each other (four or more within 350 km on a day, 8 or more in all) each had a daily PM2.5 mean of at least 25 µg/m³ and at least 2 times their usual for that time of year. Found in our own measurements, not picked by hand. How we find episodes. Values are each city's daily mean of its own monitors; causes are the usual kinds for a pattern like this, not a confirmed source.